Volume 1

Manual of mental and physical tests : a book of directions compiled with special reference to the experimental study of school children in the laboratory or classroom / by Guy Montrose Whipple.

  • Whipple, Guy Montrose, 1876-1941.
Date:
1914-1915
Catalogue details

Licence: In copyright

Credit: Manual of mental and physical tests : a book of directions compiled with special reference to the experimental study of school children in the laboratory or classroom / by Guy Montrose Whipple. Source: Wellcome Collection.

    41/392 (page 21)
    1. The Average Deviation (Mean Variation) The average deviation, A.D., of a series of measurements, m, is the arithmetical mean of their separate deviations, d, from their mean, M (or some other measure of central tendency), taken without regard to sign. Hence: j M —• m j -)— J M — m 2 | “h .I ^ ^n I A.D. or m.v. = —--? n or: d^ —(— d—|— .. . dn A.D. =-:-, n or: 2 d Al).~-. (4) n Reference to Table 1 will render this process clear: there the average right-hand grip is 283; the weakest bov has a grip of 158, hence he deviates 125 units from the average; the strongest has a grip of 508, hence he deviates 225 units from the average. The first 28 boys rank below average, and their deviations, for a reason that will be clear later, are considered in the table as minus deviations. So far as the A.D. is concerned, however, all the deviations are added without regard to sign and their sum, 3104, is divided by the number of cases, 50, yielding a mean variation of 62.1 hectograms. If the median were selected as the representative value, the variability would, of course, be computed similarly with a new series of d’s. If the individual deviations are not to be made use of subsequently, as in correlation work, a very neat short-cut to the computation of the A.D. may be made in the following manner.1 kSee Dunlap (7) for further suggestions concerning the use of the adding machine in this method.